for: Förster resonance energy transfer A fret is a raised portion on the neck of a stringed instrument, that extends generally across the full width of the neck. On most modern western instruments, frets are metal strips inserted into the fingerboard. On historical instruments and some non-European instruments, pieces of string tied around the neck serve as frets.

Frets divide the neck into fixed segments at intervals related to a musical framework. On instruments such as guitars, each fret represents one semitone in the standard western system where one octave is divided into twelve semitones.

"To fret" is often used as a verb, meaning simply "to press down the string behind a fret."

Explanation

Pressing the string against the fret reduces the vibrating length of the string to that between the bridge and the next fret between the fretting finger and the bridge. This is damped if the string were stopped with the soft fingertip on a fretless fingerboard.

An advantage of frets is that they make it much easier to achieve an acceptable standard of intonation since the positions for the correct notes are given by the frets. Furthermore, playing chords are much easier on a fretted fingerboard.

A disadvantage of using frets is that the player is restricted by the temperament given by the position of the frets. Some influence on the intonation is still possible, however. The string can be pulled to the side to increase the string tension and the pitch. This technique (commonly called 'bending') is often used by electric guitarists of all genres and is a very important part of sitar playing. On instruments with thicker frets, the string tension and pitch will vary with the pressure of the finger behind the fret. Sometimes it is also possible to pull the string toward the bridge or nut, thus lowering or raising the string tension and pitch, respectively. However, with the exception of instruments like the sitar, where extensive pulling of the string is possible, much less influence on the intonation is possible than on unfretted instruments.

Since the intonation of most modern western fretted instruments is equal tempered, the ratio of the distances of two consecutive frets to the bridge is $\backslash sqrt1\{2\}$, or approximately 1.059463. Theoretically, the twelfth fret should divide the string in two exact halves. To compensate for the increase in string tension when the string is pressed against the frets, the bridge position can be adjusted slightly so that the 12th fret plays exactly in tune.

Variations

Slanted frets: Most frets are perpendicular to the instrument's neck. Though slanted frets might be more ergonomic, few luthiers offer slanted or fanned frets; Rickenbacker offered them in the late 60's, and Novax Guitars offers such guitars today. The appearance of angled frets on these modern instruments belies the antiquity of this technique. Fanned frets first appeared on the 16th century Orpharion, a variant of the lute.